U.S. patent number 9,651,641 [Application Number 14/102,637] was granted by the patent office on 2017-05-16 for image processing apparatus, k-space generation method, magnetic resonance image apparatus, and control method of magnetic resonance image apparatus.
This patent grant is currently assigned to Beth Israel Deaconess Medical Center, Inc. (BIDMC, INC.), Samsung Electronics Co., Ltd.. The grantee listed for this patent is Beth Israel Deaconess Medical Center, Inc., Samsung Electronics Co., Ltd.. Invention is credited to Mehmet Akcakaya, Reza Nezafat, Gulaka Praveen.
United States Patent |
9,651,641 |
Praveen , et al. |
May 16, 2017 |
Image processing apparatus, K-space generation method, magnetic
resonance image apparatus, and control method of magnetic resonance
image apparatus
Abstract
A magnetic resonance (MR) image processing system includes a
data collection unit that acquires image data from a target region
of an object. A navigator unit acquires a motion signal indicating
motion comprising motion of at least a portion of an object. A data
processing unit derives k-space data for a k-space data array from
the acquired image data, by acquiring k-space data for a first
portion of the k-space from the acquired image data in response to
the motion signal indicating motion is within a predetermined range
and acquiring k-space data for a second portion of the k-space from
the acquired image data irrespective of the predetermined
range.
Inventors: |
Praveen; Gulaka (Gyeonggi-do,
KR), Akcakaya; Mehmet (Cambridge, MA), Nezafat;
Reza (Newton, MA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd.
Beth Israel Deaconess Medical Center, Inc. |
Gyeonggi-do
Boston |
N/A
MA |
KR
US |
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Assignee: |
Samsung Electronics Co., Ltd.
(Yeongtong-gu, Suwon-si, Gyeonggi-do, KR)
Beth Israel Deaconess Medical Center, Inc. (BIDMC, INC.)
(Boston, MA)
|
Family
ID: |
49765332 |
Appl.
No.: |
14/102,637 |
Filed: |
December 11, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140159724 A1 |
Jun 12, 2014 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61735674 |
Dec 11, 2012 |
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Foreign Application Priority Data
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Mar 11, 2013 [KR] |
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10-2013-0025810 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R
33/54 (20130101); G01R 33/5676 (20130101) |
Current International
Class: |
G01R
33/54 (20060101); G01R 33/567 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2004-321531 |
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Nov 2004 |
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JP |
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2006-304818 |
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Nov 2006 |
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JP |
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10-2007-0038929 |
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Apr 2007 |
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KR |
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Other References
Sachs et al., "Real-Time Motion Detection in Spiral MRI Using
Navigators", Jul. 28, 1994, Williams & Wilkins. cited by
applicant .
Weiger et al., "Motion-Adapted Gating Based on k-space Weighting
for Reduction of Respiratory Motion Artifacts", Feb. 28, 1997
Williams & Wilkins. cited by applicant.
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Primary Examiner: Bonnette; Rodney
Attorney, Agent or Firm: Cha & Reiter, LLC
Parent Case Text
CLAIM OF PRIORITY
This application claims the benefit of U.S. Provisional Patent
Application No. 61/735,674 filed on Dec. 11, 2012 in the U.S.
Patent and Trademark Office and Korean Patent Application No.
10-2013-0025810 filed on Mar. 11, 2013 in the Korean Intellectual
Property Office, the disclosure of which is incorporated herein by
reference.
Claims
What is claimed is:
1. A magnetic resonance (MR) image processing system comprising: a
data collection unit to acquire image data from a target region of
an object; a navigator unit to acquire a motion signal indicating
motion comprising motion of at least a portion of an object; and a
processor configured to determine a first portion and a second
portion of a k-space based on a user's command or a predetermined
configuration, and to derive k-space data for a k-space data array
from the acquired image data, by acquiring k-space data for the
first portion of the k-space from the acquired image data in
response to the motion signal indicating motion is within a
predetermined range and acquiring k-space data for the second
portion of the k-space from the acquired image data irrespective of
the predetermined range.
2. The image processing system according to claim 1, wherein, in
response to the motion signal indicating motion is outside the
predetermined range, the processor stops deriving the k-space data
for a portion of the k-space from the image data.
3. The image processing system according to claim 2, wherein, in
response to the processor stopping acquiring the k-space data, the
processor re-acquires image data for deriving the k-space data.
4. The image processing system according to claim 1, wherein the
predetermined range corresponds to a motion range of the at least a
portion of the object and the object comprises patient anatomy.
5. The image processing system according to claim 1, wherein the
motion of at least a portion of the object is repetitive motion and
the navigator unit tracks the repetitive motion to derive an upper
limit and a lower limit of the repetitive motion.
6. The image processing system according to claim 1, wherein a
portion of the k-space is a central area of the k-space.
7. A magnetic resonance (MR) image processing system k-space
generation method comprising: acquiring image data from a target
region of an object; acquiring a motion signal indicating motion of
at least a portion of the object; and deriving k-space data for a
k-space data array from the acquired image data by, determining
whether the motion is within a k-space data acquisition range,
determining a first portion and a second portion of the k-space
based on user's command or a predetermined configuration, receiving
the motion signal and input from a radio frequency (RF) coil unit
and only acquiring the k-space data for the first portion of the
k-space from the image data if the motion signal indication motion
is within a predetermined range; and acquiring the k-space data for
the second portion of the k-space from the image data irrespective
of the k-space data acquisition range.
8. The k-space generation method according to claim 7, further
comprising, excluding the k-space data for the portion of the
k-space in response to the motion of at least a portion of the
object deviating from the predetermined range.
9. The k-space generation method according to claim 8, further
comprising re-collecting image data for the object in response to
the motion deviating from the predetermined range.
10. The k-space generation method according to claim 7, wherein the
motion of at least a portion of the object concerns a motion range
of the object.
11. The k-space generation method according to claim 7, wherein the
motion of at least a portion of the object is repetitive motion and
the acquiring the image data comprises tracking the repetitive
motion of the object to acquire an upper limit and a lower limit of
the repetitive motion.
12. The k-space generation method according to claim 7, wherein the
first portion of the k-space is a central area of the k-space.
13. A magnetic resonance imaging system comprising: an imaging unit
to generate a static magnetic field and a gradient magnetic field
to apply to an object, to generate an electromagnetic wave to apply
to a target region of the object, and to acquire a magnetic
resonance signal generated from the target region in the object in
response to application of the electromagnetic wave to acquire
image data; a navigator unit to acquire a motion signal indicating
motion comprising motion of at least a portion of an object; and an
image generation unit configured to determine a first portion and a
second portion of a k-space based on user's command or a
predetermined configuration, and to derive k-space data for a
k-space data array from the acquired magnetic resonance signal and
to generate a magnetic resonance image based on the magnetic
resonance signal, by acquiring k-space data for the first portion
of the k-space from the acquired image data in response to the
motion signal indicating motion is within a predetermined range and
acquiring k-space data for the second portion of the k-space from
the acquired image data irrespective of the predetermined
range.
14. The magnetic resonance imaging system according to claim 13,
wherein, in response to the motion of at least a portion of an
object deviating from the predetermined range, the image generation
unit stops acquiring the k-space data from the magnetic resonance
signal.
15. The magnetic resonance imaging system according to claim 14,
wherein, in response to stopping acquiring the k-space data from
the magnetic resonance signal, the imaging generation unit
re-acquires a magnetic resonance signal.
16. The magnetic resonance imaging system according to claim 13,
wherein the motion signal indicates a motion range of the
object.
17. The magnetic resonance imaging system according to claim 13,
wherein the motion of the at least a portion of an object is
repetitive motion and the navigator unit tracks the repetitive
motion to derive an upper limit and a lower limit of the repetitive
motion.
18. The magnetic resonance imaging system according to claim 13,
wherein a portion of the k-space is a central area of the k-space
and the object comprises patient anatomy.
19. The magnetic resonance imaging system according to claim 13,
wherein the motion of the object is respiratory motion.
20. The magnetic resonance imaging system according to claim 13,
wherein the navigator unit comprises a respiratory navigator.
21. The magnetic resonance imaging system according to claim 13,
wherein the image generation unit determines whether the motion of
at least a portion of an object is within a k-space data
acquisition range using a gating window.
22. A control method of a magnetic resonance imaging system
comprising: generating a static magnetic field and a gradient
magnetic field to apply to an object; applying a radio frequency
(RF) electromagnetic wave to a target region of the object exposed
to the static magnetic field and the gradient magnetic field,
receiving a magnetic resonance signal generated from the target
region of the object in response to the radio frequency (RF)
electromagnetic wave, and tracking motion of at least a portion of
the object and providing a motion signal indicating motion
comprising motion of at least a portion of the object; determining
a first portion and a second portion of a k-space based on user's
command or a predetermined configuration; receiving the motion
signal and the magnetic resonance signal; deriving the first
portion of a k-space data from the magnetic resonance signal only
in response to the motion signal indicating motion being within a
k-space data acquisition range; and deriving k-space data for the
second portion of the k-space from the magnetic resonance signal
irrespective of the k-space data acquisition range.
23. The control method according to claim 22, wherein the deriving
the first portion of the k-space further comprises: in response to
determining whether the magnetic resonance signal corresponds to
the first portion of the k-space, determining whether the motion of
at least a portion of the object is within the k-space data
acquisition range; and in response to determining that the motion
of at least a portion of the object is within the k-space data
acquisition range, deriving k-space data for the first portion of
the k-space from the magnetic resonance signal.
24. The control method according to claim 23, further comprising
stopping acquiring the k-space data for a portion of the k-space in
response to determining that the motion of at least a portion of
the object deviates from the k-space data acquisition range.
25. The control method according to claim 24, further comprising
re-applying an electromagnetic wave to the object exposed to the
static magnetic field and the gradient magnetic field and
re-receiving a magnetic resonance signal generated from the object
in response to the motion of at least a portion of the object
deviating from the k-space data acquisition range.
26. The control method according to claim 23, wherein the
determining whether the magnetic resonance signal corresponds to
the first portion of the k-space comprises determining whether the
motion is within the k-space data acquisition range using a gating
window.
27. The control method according to claim 22, deriving the second
portion of the k-space comprises: determining whether the magnetic
resonance signal corresponds to the second portion of the k-space;
and upon determining that the magnetic resonance signal corresponds
to the second portion of the k-space, acquiring k-space data for
second portion of the k-space from the magnetic resonance
signal.
28. The control method according to claim 22, wherein the motion of
the object is respiratory motion.
29. The control method according to claim 22, wherein a portion of
the k-space is a central area of the k-space.
30. A magnetic resonance (MR) image processing system comprising: a
navigator unit to acquire a motion signal indicating motion of at
least a portion of an object; and a processor configured to
determine a first portion and a second portion of a k-space based
on user's command or a predetermined configuration, and to derive a
combined k-space data by acquiring k-space data for the first
portion of the k-space in response to the motion signal indicating
motion being within a predetermined range and acquiring k-space
data for the second portion of the k-space irrespective of the
predetermined range.
Description
BACKGROUND
1. Technical Field
A system concerns magnetic resonance (MR) image generation and
processing.
2. Description of the Related Art
An image processing apparatus generates an image which may be
easily recognized and visually confirmed by people using
predetermined raw data or performs predetermined image processing
to a portion or the entirety of the generated image, e.g. adjusts
contrast or brightness of a portion or the entirety of the
image.
The image processing apparatus may receive external image data and
perform image processing on the received image. The image
processing apparatus may include an image data collection unit to
directly capture an image. In this case, the image processing
apparatus may collect raw image data regarding the inside or
outside of an object through the image data collection unit and
process the collected raw image data to generate an image which a
user may easily view or perform predetermined image post-processing
on the generated image.
A magnetic resonance imaging (MRI) apparatus generates a processed
image for a user from raw image data using a k-space. The magnetic
resonance imaging acquires information regarding internal structure
of an object, e.g. a human body, generates a visual image based on
the acquired information, and provides the generated visual image
to a user.
SUMMARY
An image processing system rapidly and accurately generates a
k-space comprising raw data used to generate an accurate magnetic
resonance image
A magnetic resonance (MR) image processing system includes a data
collection unit that acquires image data from a target region of an
object. A navigator unit acquires a motion signal indicating motion
comprising motion of at least a portion of an object. A data
processing unit derives k-space data for a k-space data array from
the acquired image data, by acquiring k-space data for a first
portion of the k-space from the acquired image data in response to
the motion signal indicating motion is within a predetermined range
and acquiring k-space data for a second portion of the k-space from
the acquired image data irrespective of the predetermined
range.
In a feature, in response to the motion signal indicating motion is
outside the predetermined range, the data processing unit stops
deriving the k-space data for a portion of the k-space from the
image data. In response to the data processing unit stopping
acquiring the k-space data, the data collection unit re-acquires
image data for deriving the k-space data. The predetermined range
corresponds to a motion range of the at least a portion of the
object and the object comprises patient anatomy. The motion of at
least a portion of the object is repetitive motion and the
navigator unit tracks the repetitive motion to derive an upper
limit and a lower limit of the repetitive motion. A portion of the
k-space is a central area of the k-space.
In another feature, a magnetic resonance (MR) image processing
system k-space generation method comprises acquiring image data
from a target region of an object and acquiring a motion signal
indicating motion comprising motion of at least a portion of the
object. K-space data is derived for a k-space data array from the
acquired image data by, in response to determining whether the
motion is within a k-space data acquisition range, acquiring the
k-space data for a first portion of the k-space from the image data
and acquiring the k-space data for a second portion of the k-space
from the image data irrespective of the k-space data acquisition
range. The method excludes acquiring the k-space data for a portion
of the k-space in response to the motion of at least a portion of
the object deviating from the k-space data acquisition range and
re-collects image data for the object in response to the motion
deviating from the k-space data acquisition range. The motion of at
least a portion of the object concerns a motion range of the object
and is repetitive motion and the acquiring the image data comprises
tracking the repetitive motion of the object to acquire an upper
limit and a lower limit of the repetitive motion. A portion of the
k-space is a central area of the k-space and the object comprises
patient anatomy.
In a further feature, a magnetic resonance imaging system includes
an imaging unit to generate a static magnetic field and a gradient
magnetic field to apply to an object, to generate an
electromagnetic wave to apply to a target region of the object, and
to acquire a magnetic resonance signal generated from the target
region in the object in response to application of the
electromagnetic wave to acquire image data. A navigator unit
acquires a motion signal indicating motion comprising motion of at
least a portion of an object. An image generation unit derives
k-space data for a k-space data array from the acquired magnetic
resonance signal and generates a magnetic resonance image based on
the magnetic resonance signal, by acquiring k-space data for a
first portion of the k-space from the acquired image data in
response to the motion signal indicating motion is within a
predetermined range and acquiring k-space data for a second portion
of the k-space from the acquired image data irrespective of the
predetermined range.
In yet another feature, in response to the motion of at least a
portion of an object deviating from the predetermined range, the
image generation unit stops acquiring the k-space data from the
magnetic resonance signal and in response to stopping acquiring the
k-space data from the magnetic resonance signal, the imaging unit
re-acquires a magnetic resonance signal. The motion signal
indicates a motion range of the object and the motion of the at
least a portion of an object is repetitive motion and the navigator
unit tracks the repetitive motion to derive an upper limit and a
lower limit of the repetitive motion. Also a portion of the k-space
is a central area of the k-space and the object comprises patient
anatomy and the motion of the object is respiratory motion.
Further, the navigator unit comprises a respiratory navigator and
the image generation unit determines whether the motion of at least
a portion of an object is within the k-space data acquisition range
using a gating window.
In an additional feature, a control method of a magnetic resonance
imaging system comprises generating a static magnetic field and a
gradient magnetic field to apply to an object. The method applies a
radio frequency (RF) electromagnetic wave to a target region of the
object exposed to the static magnetic field and the gradient
magnetic field, receives a magnetic resonance signal generated from
the target region of the object in response to the radio frequency
(RF) electromagnetic wave, and tracks motion of at least a portion
of the object and provides a motion signal indicating motion
comprising motion of at least a portion of the object. The method
derives a first portion of a k-space data from the magnetic
resonance signal in response to the motion signal indicating motion
being within a k-space data acquisition range and derives k-space
data for a second portion of the k-space from the acquired image
data irrespective of the k-space data acquisition range. In
response to determining whether the magnetic resonance signal
corresponds to a predetermined portion of the k-space, the method
determines whether the motion of at least a portion of the object
is within the k-space data acquisition range and in response to
determining that the motion of at least a portion of the object is
within the k-space data acquisition range, the method derives
k-space data for the predetermined portion of the k-space from the
magnetic resonance signal.
In yet a further feature, the method includes re-applying an
electromagnetic wave to the object exposed to the static magnetic
field and the gradient magnetic field and re-receiving a magnetic
resonance signal generated from the object in response to the
motion of at least a portion of the object deviating from the
k-space data acquisition range. The determining whether the
magnetic resonance signal corresponds to the predetermined portion
of the k-space comprises determining whether the motion information
is within the k-space data acquisition range using a gating window.
The method also includes determining whether the magnetic resonance
signal corresponds to a predetermined portion of the k-space and
upon determining that the magnetic resonance signal corresponds to
another portion of the k-space different from the predetermined
portion of the k-space, acquiring k-space data for another portion
of the k-space from the magnetic resonance signal.
BRIEF DESCRIPTION OF THE DRAWINGS
These and/or other aspects of the invention will become apparent
and more readily appreciated from the following description of the
embodiments, taken in conjunction with the accompanying drawings of
which:
FIG. 1 shows a data processing unit of an image processing
apparatus according to invention principles;
FIG. 2 shows an image processing apparatus according to invention
principles;
FIG. 3 shows a data collection unit according to invention
principles;
FIG. 4 shows a navigator unit according to invention
principles;
FIG. 5 shows motion information output in an image from the
navigator unit according to invention principles;
FIG. 6 shows the image processing apparatus in detail according to
invention principles;
FIG. 7 shows a k-space according to invention principles;
FIG. 8 shows motion information output from the navigator unit
according to invention principles;
FIG. 9 shows an image processing apparatus in detail according to
invention principles;
FIG. 10 shows a k-space acquired based on k-space data collected
from a first area and a second area according to invention
principles;
FIG. 11 shows an example of the k-space according to invention
principles;
FIG. 12 shows a magnetic resonance imaging apparatus according to
invention principles;
FIG. 13 shows a magnetic resonance imaging system according to
invention principles;
FIG. 14 shows a magnetic resonance imaging apparatus in detail
according to invention principles;
FIG. 15 shows a static magnetic field of the magnetic resonance
imaging apparatus according to invention principles;
FIG. 16 shows a gradient magnetic field coil unit of the magnetic
resonance imaging apparatus according to invention principles;
FIG. 17 shows pulse sequences of gradient coils according to
invention principles;
FIG. 18 shows a k-space data processing unit of the magnetic
resonance imaging apparatus according to invention principles;
FIG. 19 shows another k-space data processing unit of the magnetic
resonance imaging apparatus according to invention principles;
FIG. 20 shows a k-space data processing unit of the magnetic
resonance imaging apparatus according to invention principles;
FIG. 21 and FIG. 22 show MR images generated by the system
according to invention principles;
FIG. 23 shows a k-space generation method according to invention
principles;
FIG. 24 shows another k-space generation method according to
invention principles;
FIG. 25 shows a control method of the magnetic resonance imaging
apparatus according to invention principles;
FIG. 26 shows a control method of the magnetic resonance imaging
apparatus according to invention principles; and
FIG. 27 shows a control method of the magnetic resonance imaging
apparatus according to invention principles.
DETAILED DESCRIPTION
Reference will now be made in detail to the embodiments of the
present invention, examples of which are illustrated in the
accompanying drawings, wherein like reference numerals refer to
like elements throughout.
Hereinafter, an embodiment of an image processing apparatus is
described with reference to FIGS. 1 to 11.
FIG. 1 shows a data processing unit 100 of an image processing
apparatus that receives collected raw data, acquires k-space data
from the raw data, fills a k-space using the acquired k-space data
to generate the k-space, and outputs the k-space. The data
processing unit 100 may divide the k-space into a plurality of
areas and perform different processes in the respective areas on
the acquired k-space data to provide k-space for output. For
example, in a case in which the data processing unit 100 selects
and acquires k-space data from a plurality of areas, k-space data
may be selected and acquired on the premise that at least one of
the areas satisfies a predetermined condition. In this case, the
data processing unit 100 may further acquire additional information
and select and acquire k-space data depending upon whether the
additionally acquired information satisfies a predetermined
condition or an additionally calculated condition. The additionally
acquired information may be information regarding motion of a
motion region, i.e. motion information (NAV data). As shown in FIG.
1, the data processing unit 100 may further receive the motion
information regarding the motion region independent of the raw data
and select k-space data based on the received motion information to
generate a k-space.
The data processing unit 100 may divide the k-space into the
plurality of areas and collect k-space data for the k-space from
the respective areas according to a predetermined condition or
unconditionally. For example, it is assumed that the k-space may be
divided into two areas. Such division may be predetermined,
selected by a user during operation of the data processing unit
100, or determined according to additionally input data or external
environmental variables. Consequently, the data processing unit 100
may select and acquire k-space data from the two divided areas
using different methods. For example, the data processing unit 100
may acquire k-space data from one area of the k-space on the
premise that a first predetermined condition is satisfied and
collect k-space data from the other area of the k-space on the
premise of a different second predetermined condition is satisfied
or no condition is satisfied. The collected k-space data may be
combined to generate one k-space.
In order to acquire k-space data in divided areas of the k-space,
the data processing unit 100 may acquire the k-space data from the
respective areas of the k-space at the same time or at different
times. In addition, the data processing unit 100 may sequentially
acquire the k-space data from the respective areas in predetermined
order. For example, where the k-space is divided into a first area
and a second area, the data processing unit 100 may further include
a first processing unit and a second processing unit to extract
k-space data from the first area and the second area. The first
processing unit and the second processing unit may acquire the
k-space data at the same time or at different times. The first
processing unit may extract the k-space data from the first area
and subsequently the second processing unit may extract the k-space
data from the second area.
An image processing apparatus including the data processing unit
100 is shown in FIG. 2. The image processing apparatus may include
a data collection unit 10, a navigator unit 20, the data processing
unit 100, and an image processing unit 30. The data collection unit
10 collects information regarding a target region outside or inside
an object ob. FIG. 3 shows the data collection unit. The data
collection unit 10 collects a signal generated from the target
region to collect information regarding the target region and
outputs the collected information, i.e. the signal, in the form of
raw data after amplifying the collected information or performing
analog/digital conversion to the collected information. The data
collection unit 10 may output a plurality of signals (signal A to
signal C). The output signals are transmitted to the data
processing unit 100 as shown in FIG. 2.
The data collection unit 10 may be a magnetic field forming coil
and a radio frequency (RF) coil to collect slice information of the
interior of an object, such as a human body, from the object in a
bore of a magnetic resonance image apparatus. The data collection
unit 10 may collect a magnetic resonance signal and output the
collected magnetic resonance signal. The output magnetic resonance
signal may be amplified and may be output in the form of raw data
without additional processing. The navigator unit 20 tracks motion
of a motion region of the object ob to collect motion information
(NAV data) regarding motion of the object ob. In this case, the
object having the tracked motion region may be identical to or
different from the object having the target region. FIG. 4 shows
the navigator unit 20 including a sensor unit 21 and a motion
information storage unit 22.
The sensor unit 21 senses motion of the object ob, specifically
motion of the motion region of the object ob. For example, in a
case in which the object ob is a human body, the sensor unit 21
senses and tracks motion of the motion region of the object ob, for
example motion of a chest of the human body ob, such as respiration
of the human body, or pulsation of a heart in the human body. The
motion region may be identical to or different from the target
region. In an example, the target region and the motion region may
be a chest including a lung. In another example, the target region
may be a heart and internal organs, whereas the motion region may
be a lung, a liver, and a diaphragm. This may be determined
according to user selection or predetermined setting. In addition,
the motion region and the target region may be tissue or structure
of the same object ob. For example, the motion region may be the
diaphragm of one human body and organs and the target region may be
various internal organs, such as the heart and the lung, of the
same human body. As needed, the motion region and the target region
may be tissue or structure of different objects ob.
The sensor unit 21 senses and tracks motion of the motion region to
output a signal, i.e. motion information (NAV data), corresponding
to the motion of the object ob. The output motion information may
be information regarding a motion range of the motion region, for
example the upper limit and the lower limit of motion of the chest
during respiration. Specifically, in a case in which motion of the
motion region is respiration, i.e. repetitive motion including
inhalation and exhalation, the sensor unit 21 may track the
repetitive motion of the object ob to collect information regarding
the upper limit and the lower limit of the repetitive motion of the
object and output the collected information as motion information
(NAV data). The motion information (NAV data) output from the
sensor unit 21 may be raw data. Although not shown, therefore, the
navigator unit 20 may further include a motion information
processing unit to process the motion information output from the
sensor unit 21 to generate processed data, such as image data
enabling to visually identify the motion.
The motion information storage unit 22 temporarily and continuously
stores the motion information output from the sensor 21 or the
motion information processing unit (within unit 22) according to
the motion of the motion region. The motion information storage
unit 22 transmits the stored motion information (NAV data) to the
data processing unit 100. The image processing apparatus is a
magnetic resonance imaging apparatus, the navigator unit 20 may be
a respiratory navigator. The respiratory navigator tracks
respiration using at least one navigation echo output according to
motion of the chest due to external respiration. Motion information
output from the respiratory navigator may be imaged as shown in
FIG. 5 and output in a form intuitively recognizable by a user.
FIG. 5 shows a motion information output from the navigator unit
comprising an image acquired using coronary artery MR imaging of a
chest using respiratory gating. The dark portion of the upper end
of the image indicates a lung and the bright portion of the lower
end of the image indicates a liver. Time advances from the left
side to the right side of the image. A wave motion form is present
at an interface between the lung and the liver. In this case,
upwardly convex portions of the image indicate shrinkage of the
lung, i.e. exhalation, and the downwardly concave portions of the
image indicate expansion of the lung, i.e. inhalation. The wave
motion form is present at the interface between the lung and the
liver due to change in size of the lung and liver according to
respiration or motion of the diaphragm between the lung and liver.
Consequently, motion of the diaphragm, i.e. respiration, may be
tracked and confirmed from coronary artery MR images acquired by a
plurality of navigation echoes output over time.
As shown in FIG. 2, the data processing unit 100 receives data from
the data collection unit 10 and the navigator unit 20, acquires
k-space data using the received data, and transmits the acquired
k-space data, i.e. the k-space, to the image processing unit 30.
Specifically, the data processing unit 100 receives raw data from
unit 10 used to generate a k-space data array for generating an
image, and receives motion information regarding motion of the
motion region, such as respiration, i.e. repetitive motion of the
diaphragm, from the navigator unit 20. The data processing unit 100
may include a first area processing unit 110, a second area
processing unit 120, and an area combination unit 130 as shown in
FIG. 2. As described above, the data processing unit 100 may
collect k-space data from areas of a k-space to be generated.
FIG. 6 shows the image processing apparatus and FIGS. 2 and 6 show
the image processing apparatus in a case in which the data
processing unit 100 divides a k-space into two areas, i.e. a first
area and a second area, and separately acquires k-space data from
the respective areas, i.e. the first area and the second area, to
generate the k-space. The data processing unit 100 may include a
first area processing unit 110, a second area processing unit 120,
and an area combination unit 130. The first area processing unit
110 and the second area processing unit 120 acquire k-space data
corresponding to different areas of the k-space from raw data. In
addition, the first area processing unit 110 and the second area
processing unit 120 may acquire k-space data according to different
conditions or different methods.
FIG. 7 shows a data space expressed as a matrix and acquired based
on raw data sg1 to sg7 of the magnetic resonance imaging apparatus.
The data space may comprise a k-space data array matrix of
256.times.256. The middle row of the matrix of the data space
corresponds to a signal acquired in a state in which a
phase-encoding gradient is the minimum. Rows of the matrix arranged
from the middle to the edges of the data space correspond to
signals acquired while the phase-encoding gradient is gradually
increased. The data space may be divided into a plurality of areas,
for example a set of a plurality of rows located at the central
portion of the data space, comprises a first data area c1, and the
remaining portion of the data space corresponding to the k-space,
for example a set of the remaining rows excluding the rows located
at the central portion of the data space, comprises a second data
area c2a and c2b. The set of rows located at the central portion of
the data space may include a center of the data space. The central
area of the data space corresponds to a central area of the
k-space.
The first area processing unit 110 acquires k-space data
corresponding to the first area of the k-space from raw data sg3 to
sg5 corresponding to the first area of the k-space. In other words,
the first area processing unit 110 acquires k-space data to fill
the first area of the k-space from the first data area c1 of the
k-space shown in FIG. 7. The second area processing unit 120
acquires k-space data corresponding to the second area of the
k-space from raw data sg1, sg2, sg6, and sg7 corresponding to the
second area of the k-space. The second area processing unit 120
acquires k-space data to fill the second area of the k-space from
the second data area c2 (C2a and C2b) of the k-space shown in FIG.
7.
The first area processing unit 110 of the data processing unit 100
may acquire k-space data corresponding to the first area of the
k-space from raw data in a case in which a predetermined condition
is satisfied. The predetermined condition may be a condition based
on motion information (NAV signal) output, for example, from the
navigator unit 20. Specifically, as shown in FIGS. 2 and 6, the
first area processing unit 110 may receive raw data from the data
collection unit 10 and motion information from the navigator unit
20. The first area processing unit 110 determines whether to
acquire k-space data based on the motion information received from
the navigator unit 20 and acquires k-space data from the raw data
resulting response to the determination. The first area processing
unit 110 may include an area determination unit 111, a motion
information determination unit 112, and a data acquisition unit
113.
The area determination unit 111 determines whether the raw data
received from the data collection unit 10 is data for an area of
the k-space to be processed by the first area processing unit 110,
e.g. the first area of the k-space. The area of the k-space may be
predetermined, selected by a user, or calculated based on
additional information, such as raw data or motion information.
When the area determination unit 111 determines that the raw data
received from the data collection unit 10 are signals corresponding
to an area of the k-space to be processed by the first area
processing unit 110, e.g. the first area of the k-space, the motion
information determination unit 112 determines whether to acquire
data based on the motion information received from the navigator
unit 20. For example, where the object ob is a human body, the
motion information determination unit 112 may determine whether to
acquire k-space data in response to respiration of the human body.
Where the chest is excessively expanded due to respiration of the
human body when acquiring an image, the acquired image may be
erroneous. In this case, therefore, the motion information
determination unit 112 may determine not to acquire k-space data
such that the first area processing unit 110 does not acquire the
k-space data. The motion information determination unit 112
determines not to acquire k-space data in a case in which motion
information, such as a motion range, of the motion region is out of
a predetermined range. Also, the motion information determination
unit 112 determines to acquire k-space data in a case in which the
motion information, such as the motion range, of the motion region
is within the predetermined range.
FIG. 8 shows motion information output from the navigator unit 20.
Motion information output from the navigator unit 20 is transmitted
to the motion information determination unit 112. The motion
information determination unit 112 may compare input motion
information signals NAV1 and NAV2 with a predetermined k-space data
acquisition range NAV and determine whether the first area
processing unit 110 acquires a signal input to the first data area
c1 to generate the k-space based on a comparison result.
Specifically, where the motion information does not deviate from
the k-space data acquisition range as shown in the left side NA of
FIG. 8 (NAV1), the motion information determination unit 112 may
determine to acquire k-space data based on the motion information,
extract a signal from input raw data to generate a control signal
to acquire k-space data to generate the k-space, and transmit the
control signal to the data acquisition unit 113.
Where the motion information deviates from the k-space data
acquisition range as shown in the right side NB of FIG. 8 (NAV2),
the motion information determination unit 112 may determine not to
acquire k-space data based on the motion information, generate a
control signal not to extract a signal from input raw data, i.e. a
control signal not to acquire k-space data, and transmit the
control signal to the data acquisition unit 113. Where the motion
information deviates from the k-space data acquisition range (NAV2)
and the motion information determination unit 112 determines not to
acquire k-space data based on the motion information, the motion
information determination unit 112 may generate additional
information regarding a determination result or a control signal
based on the determination result and transmit the information or
the control signal to the controller 40.
Upon receiving the information or the control signal from the
motion information determination unit 112, the controller 40
generates an additional control signal for the data collection unit
10 or the navigator unit 20 and transmits the generated control
signal to the data collection unit 10 or the navigator unit 20. The
data collection unit 10 collects raw data from the target region
according to the control signal received from the controller 40 and
transmits the collected data to the first area processing unit 110
or the second area processing unit 120 of the data processing unit
100. The data collection unit 10 may continuously collect raw data
from the target region without an additional control signal. In
addition, the navigator unit 20 collects motion information from
the motion region according to the control signal received from the
controller 40 and transmits the collected motion information to the
first area processing unit 110 of the data processing unit 100. The
navigator unit 20 may continuously collect motion information from
the motion region without an additional control signal. In this
case, the navigator unit 20 continuously performs a motion
information collection operation irrespective of a control
signal.
The first area processing unit 110 acquires or does not acquire
k-space data for the first area of the k-space based on the raw
data and the motion information received from the data collection
unit 10 and the navigator unit 20. The data acquisition unit 113
acquires or does not acquire k-space data according to the control
signal received from the motion information determination unit 112.
For example, when the motion information determination unit 112
determines that the motion information is within a predetermined
data acquisition range, generates a control signal to acquire
k-space data from the raw data, and transmits the generated control
signal to the data acquisition unit 113, the data acquisition unit
113 stores data of the first data area c1 to acquire k-space data
for the first area of the k-space.
When the motion information determination unit 112 determines that
the motion information is out of the predetermined data acquisition
range, unit 112 transmits a control signal not to acquire k-space
data to the data acquisition unit 113, the data acquisition unit
113 does not extract or store data of the first data area c1. As a
result, the data acquisition unit 113 does not acquire k-space data
for the first area of the k-space from the raw data. The data of
the first data area c1 is discarded. The second area processing
unit 120 acquires k-space data using a method different from the
method used in the first area processing unit 110.
FIG. 9 shows the image processing apparatus including the second
area processing unit 120 also including an area determination unit
121 and a data acquisition unit 122. The area determination unit
121 of the second area processing unit 120 determines whether the
raw data received from the data collection unit 10 is data for an
area of the k-space to be processed by the second area processing
unit 120, e.g. the second area of the k-space. In the same manner
as in the first area of the k-space, the second area of the k-space
may be predetermined, selected by a user, or determined based on
additional information, such as raw data or motion information.
When the area determination unit 121 determines that the raw data
received from the data collection unit 10 is data to be processed
by the second area processing unit 120, the data acquisition unit
122 stores the raw data to acquire k-space data for the second area
of the k-space.
Unlike the first area processing unit 110, the second area
processing unit 120 does not determine whether additional motion
information is included in the k-space data acquisition range and
unconditionally acquires k-space data. Although not shown, the data
processing unit 100 may further include an area division unit to
sort a data signal corresponding to the first area processed by the
first area processing unit 110 and a data signal corresponding to
the second area to be processed by the second area processing unit
120 before the first area processing unit 110 and the second area
processing unit 120 acquire k-space data. The area division unit
sorts data input from the data collection unit 10 and transmits the
sorted data to the first area processing unit 110 or the second
area processing unit 120.
Specifically, when an area decision unit 140 determines areas of
the k-space to be processed by the first area processing unit 110
and the second area processing unit 120 according to a user command
input through a manipulation unit or pre-stored setting
information, the area division unit sorts raw data corresponding to
the first area of the k-space and raw data corresponding to the
second area of the k-space from raw data input from the data
collection unit and transmits the sorted raw data to the first area
processing unit 110 and the second area processing unit 120. The
area division unit determines whether the raw data corresponds to
the first area of the k-space and if so, transmits the raw data to
the first area processing unit 110. Upon determining that the raw
data does not correspond to the first area of the k-space, the area
division unit determines whether the raw data correspond to the
second area of the k-space and if so, transmits the raw data to the
second area processing unit 120. The area combination unit 130 of
the data processing unit 100 combines the k-space data for the
first area acquired by the first area processing unit 110 and the
k-space data for the second area acquired by the second area
processing unit 120 to form an overall k-space.
FIG. 10 shows a k-space generated based on the k-space data
collected from the first area and the second area and FIG. 11 shows
a three-dimensional view of the k-space. Referring to FIG. 10, the
finally generated k space K may be divided into three areas, i.e. a
first area to a third area K1 to K3. The first area K1 and the
third area K3 of the k-space K are filled with the k-space data
acquired by the second area processing unit 120. The second area K2
is filled with the k-space data acquired by the first area
processing unit 110. As a result, the k-space as shown in FIG. 11
is generated. The generated k-space is used for image generation
and is transmitted to the image processing unit 30 as shown in
FIGS. 2, 6, and 9.
The data processing unit 100 may further include an area decision
unit 140 (FIG. 9) to determine areas, such as the first area and
the second area, of the k-space. The area decision unit 140 may
receive information regarding areas of the k-space to be processed
by the respective area processing units 110 and 120 through an
additional external workstation. Alternatively, the area decision
unit 140 may read information regarding areas of the k-space from
an additional memory device R to determine the areas of the
k-space. Specifically, the information regarding the areas of the
k-space may include information, such as the number of areas, the
size of each area, and position of each area.
The first area processing unit 110 and the second area processing
unit 120 may further include the area determination units 111 and
121, respectively. The area decision unit 140 determines areas,
e.g. the first area and the second area, of the k-space and
transmits decision information to the area determination unit 111
of the first area processing unit 110 or the area determination
unit 121 of the second area processing unit 120. The area
determination unit 111 of the first area processing unit 110 or the
area determination unit 121 of the second area processing unit 120
determines whether the input raw data corresponds to the area, e.g.
the first area K2 or the second area K1 and K3, processed by the
first area processing unit 110 or the second area processing unit
120 based on the information regarding the area of the k-space
received from the area decision unit 140 and acquires k-space data
for the first area K2 or the second area K1 and K3 of the k-space
in response to a determination result.
The image processing unit 30 shown in FIGS. 2, 6, and 9 generates a
predetermined image based on the k-space received from the data
processing unit 100. The image processing unit 30 may perform
Fourier transform to the received k-space to generate a magnetic
resonance image. Although the k-space is divided into two areas,
the k-space may be divided into more than two areas. In this case,
the data processing unit 100 may further include a third area
processing unit or a fourth area processing unit. The image
processing apparatus as described above may be applied to various
imaging systems. For example, the image processing apparatus may be
applied to a magnetic resonance imaging apparatus.
A magnetic resonance imaging apparatus is described with reference
to FIGS. 12 to 23. FIG. 12 shows a magnetic resonance imaging
apparatus including a data collection unit 200, an amplifier 920,
an analog/digital (A/D) converter 930, an image generation unit
500, a navigator 400, and a display unit d. The data collection
unit 200 collects a magnetic resonance signal such as analog
signal, from a target region in an object ob to generate a magnetic
resonance image. The amplifier 920 amplifies the collected magnetic
resonance signal and transmits the amplified magnetic resonance
signal to the A/D converter 930. The A/D converter 930 converts the
amplified analog magnetic resonance signal into a digital signal.
The digitized signal is transmitted to the image generation unit
500. The image generation unit 500 generates a k-space data array
from the digitized magnetic resonance signal using a k-space data
processing unit 600 and an image processing unit 520 and performs
Fourier transform on the k-space data to generate a magnetic
resonance image.
The k-space data processing unit 600 generates a k-space data array
based on the digitized magnetic resonance signal. The k-space data
processing unit 600 may acquire k-space data for a portion of the
k-space and k-space data for another portion of the k-space using
different methods. The k-space data processing unit 600 may further
receive motion information regarding motion of a motion region of
the object ob from the navigator 400. The k-space data processing
unit 600 may acquire k-space data for a portion of the k-space
based on the received motion information. In addition, the k-space
data processing unit 600 may acquire k-space data for another
portion of the k-space irrespective of the motion information.
The image processing unit 520 of the image generation unit 500
performs a Fourier transform on the k-space data generated by the
k-space data processing unit 600 to generate a magnetic resonance
image and transmits the magnetic resonance image to the display
unit d under control of a central processing unit or a user. The
display unit d displays the magnetic resonance image to the user.
FIG. 13 shows the magnetic resonance imaging apparatus and FIG. 14
shows the magnetic resonance imaging apparatus in more detail.
As shown in FIG. 13, the magnetic resonance imaging apparatus
includes a bore, which is a cylindrical body having a hollow inner
space, i.e. a cavity. An object, e.g. a human body, is introduced
into the cavity while being placed on a transfer unit, e.g. a
transfer table. The data collection unit 200 generates a magnetic
field at the object in the cavity to induce magnetic resonance
excitation and receives a magnetic resonance signal generated in
response to the magnetic resonance excitation to collect raw data
of a slice in the object. The data collection unit 200 of the
magnetic resonance imaging apparatus collects a magnetic resonance
signal from the object ob in response to atomic nucleus resonance
induced by an electromagnetic wave of a predetermined frequency,
i.e. a nuclear magnetic resonance (NMR) phenomenon. An atomic
nucleus of an element, such as hydrogen (H), phosphorus (P), sodium
(Na), or each carbon isotope (C), has a spin. When the atomic
nucleus is exposed to an external magnetic field, such as a static
magnetic field, and thus magnetized, the spin of the atomic nucleus
is aligned in a magnetic field direction and, in addition, rapidly
rotates at a predetermined angle to a central axis due to torque
applied by the magnetic field, i.e. performs precession. A
frequency of the precession of the spin of the atomic nucleus is
referred to as a Larmor frequency. The Larmor frequency may be
changed depending upon intensity of the external magnetic field and
type of the atomic nucleus. When an electromagnetic wave having a
frequency identical or similar to the Larmor frequency is applied
to an atomic nucleus, e.g. an atomic nucleus of a hydrogen atom,
during precession, a magnetization vector of the atomic nucleus
resonates and thus is directed in a direction perpendicular to the
static magnetic field. At this time, the magnetization vector
induces a voltage signal, which is generally called a free
induction decay (FID) signal, in a radio frequency (RF) coil
adjacent thereto. This is referred to as a NMR phenomenon.
The data collection unit 200 generates an image of a target region
in the object, e.g. a human body, from the induced voltage signal
and provides the generated image to a user. In order to acquire a
magnetic resonance signal using the NMR phenomenon as described
above, as shown in FIGS. 13 and 14, the data collection unit 200
may include a plurality of coil units, i.e. a static magnetic field
coil unit 210, a gradient magnetic field coil unit 220, and an RF
coil unit 230. The coil units may be formed at the bore as shown in
FIG. 13. FIG. 15 shows a static magnetic field of the magnetic
resonance imaging apparatus generated by the static magnetic field
coil unit. The static magnetic field coil unit 210 generates a
static magnetic field to magnetize an atomic nucleus of an element,
such as hydrogen, phosphorus, or sodium, to induce an MR phenomenon
among elements present in the human body. The static magnetic field
generated by the static magnetic field coil unit 210 is generally
parallel to a coaxial line of the bore.
On the assumption that a component parallel to the coaxial line of
the bore is a z axis, a component perpendicular to the z axis and
parallel to the transfer table is an x axis, and a component
perpendicular to the z axis and parallel to a normal line of the
transfer table is a y axis as shown in FIG. 15, the static magnetic
field is generated in the z-axis direction of FIG. 15. The object
ob is a human body, the static magnetic field is generated from the
head to the feet of the human body. The Larmor frequency is
proportional to intensity of the static magnetic field generated in
the object ob. The static magnetic field coil unit 210 is made of a
superconductive electromagnet or a permanent magnet. The
superconductive electromagnet is used to generate a magnetic field
having a high magnetic flux density of 0.5 T. When an atomic
nucleus of an element, such as hydrogen, phosphorus, or sodium, is
exposed to the static magnetic field, the atomic nucleus is
magnetized and a magnetization vector of the atomic nucleus
performs precession about the static magnetic field.
The gradient magnetic field coil unit 220 generates spatially
linear gradient magnetic fields Gx, Gy, and Gz at the object ob in
the cavity to change equality of the magnetic field. When the
magnetization vector of the atomic nucleus of the element, such as
hydrogen, phosphorus, or sodium, generated by the primary magnetic
field is rotated on a transverse plane, therefore, gradient coils
221 to 223 (FIG. 16) spatially control a rotational frequency or
phase of the magnetization vector such that a magnetic resonance
image signal is expressed as a spatial frequency area, i.e. a
k-space.
FIG. 16 shows the gradient magnetic field coil unit of the magnetic
resonance imaging apparatus. As shown in FIG. 16, the gradient
magnetic field coil unit 220 may include three kinds of gradient
coils 221 to 223 to generate gradient magnetic fields in x-axis,
y-axis, and z-axis directions. The respective gradient coils
generate gradient magnetic fields Gx, Gy, and Gz in different
directions. The z-axis gradient coils 221 generate a slice-select
gradient magnetic field Gz in the z-axis direction to select a
slice used in selecting a slice. The y-axis gradient coils 222
generate a phase-encoding gradient magnetic field Gy in the y-axis
direction to cause a phase shift such that rows of the slice have
different phases for phase encoding. The x-axis gradient coils 223
generate a frequency-encoding gradient magnetic field Gy in the
x-axis direction to distinguish between spins constituting the
respective rows such that the spins have different frequencies.
FIG. 17 shows pulse sequences for driving the gradient coils. The
z-axis gradient coils 221 generate a gradient magnetic field Gz in
the z-axis direction. For example, in a case in which the object ob
is a human body, intensity of a magnetic field is gradually
decreased from the head to the feet of the human body to generate a
magnetic field having a predetermined gradient in the z-axis
direction. In this case, when the RF coil unit 230 transmits an RF
pulse, a magnetic resonance signal is generated from a selected
anatomical slice. Spins of protons of the selected slice have the
same frequency and phase with the result that distinction between
the respective spins may be ambiguous.
The y-axis gradient coils 222 generate a phase-encoding gradient
magnetic field Gy in the y-axis direction. Different phase shifts
are applied to spins of each slice in response to the
phase-encoding gradient magnetic field. That is, when a y-axis
gradient magnetic field is generated, the phase of the spins to
which a high gradient magnetic field is applied is changed to
correspond to a high frequency and the phase of the spins to which
a low gradient magnetic field is applied is changed to correspond
to a low frequency. When the y-axis gradient magnetic field is
blocked, the spins process at a predetermined frequency and
permanent phase change is generated due to the y-axis gradient
magnetic field, thereby distinguishing between the respective spins
in a phase encoding process. During acquisition of the magnetic
resonance signal, the x-axis gradient coils 223 apply an x-axis
frequency-encoding gradient magnetic field Gx to the object ob. In
a slice expressed as a predetermined matrix, proton spins
corresponding to the respective matrix rows have different
frequencies enabling distinguishing between the spins. This is
called frequency encoding.
In response to application of the static magnetic field and the
gradient magnetic field to the object ob, the RF coil unit 230
generates a high frequency magnetic field to rotate a magnetization
vector generated by the static magnetic field on a transverse
plane. When high frequency current of a Larmor frequency band is
applied to the RF coil unit 230, a high frequency coil of the RF
coil unit 230 generates a magnetic field rotating around the coil
at a Larmor frequency according to the applied high frequency
current. At this time, when the rotating magnetic field resonates
with the magnetization vector of the target region in the object
ob, the magnetization vector of the target region rotates at the
Larmor frequency in parallel to the transverse plane. At this time,
electromotive force is induced in the high frequency coil of the RF
coil unit 230 according to the rotation of the magnetization
vector. A sine wave of the Larmor frequency is demodulated based on
the induced electromotive force signal to acquire a magnetic
resonance signal of a baseband, thereby a magnetic resonance signal
is acquired for the target region inside or outside the object ob.
The RF coil unit 230 may use a series of high frequency coils to
generate a rotating magnetic field and to receive a magnetic
resonance signal. Alternatively, the RF coil unit 230 may include a
high frequency coil to generate rotating magnetic field and another
high frequency coil to receive a magnetic resonance signal.
Referring to FIGS. 12 and 14, the magnetic resonance imaging
apparatus may include a navigator 400 that tracks motion of the
object ob, specifically motion of the motion region of the object
ob. The navigator 400 may be a respiratory navigator to detect and
track respiration of the human body using at least one navigation
echo output in response to the respiration of the human body and
output motion information, such as a navigator echo, as shown in
FIG. 5. For example, as shown in FIG. 5, the diaphragm between the
lung and liver in the chest may shrink or expand within a
predetermined motion range. The navigator 400 may track motion of
the diaphragm and the surroundings and output a wave motion form at
the interface between the lung and the liver as motion information
(NAV data). The motion information, such as a navigation echo, may
comprise an additional RF pulse signal and gradient added to
different kinds of pulse sequences to monitor the target region
using MR images. The navigation echo may be used in free breathing
MRI in a free breathing state, such as cardiac MR imaging. The
output motion information is transmitted to the k-space data
processing unit 600 of the image generation unit 500.
As shown in FIG. 14, the magnetic resonance imaging apparatus may
further include a controller 300 that generates a control signal to
control operation of the data collection unit, i.e. unit 200. The
controller 300 may include a static magnetic field controller 310
to control the static magnetic field coil unit 210, a gradient
magnetic field controller 320 to control the gradient magnetic
field coil unit 220, and an RF coil controller 330 to control the
RF coil unit 230. The static magnetic field controller 310 of the
controller 300 generates a control signal according to user
instruction or command input through a manipulation unit i, such as
an external workstation w, or prestored setting and transmits the
control signal to a static magnetic field coil application unit
311.
Upon receiving the control signal, the static magnetic field coil
application unit 311 applies current to the static magnetic field
coil unit 210 such that the static magnetic field coil unit 210 and
the gradient magnetic field coil unit 220 generate a static
magnetic field. In the same manner, the gradient magnetic field
controller 320 and the RF coil controller 330 generate a plurality
of control signals according to user instruction or command or
prestored setting and transmit the generated control signals to a
gradient magnetic field coil application unit 321 and an RF coil
application unit 331 such that the gradient magnetic field coil
unit 220 and the RF coil unit 230 generate a gradient magnetic
field or an electromagnetic wave for the object ob or the target
region in the object ob. In addition, the controller 300 may
further include a navigator controller 340 to control operation of
the navigator 400 by generating a control signal to start or stop
operation of the navigator 400 and transmits the generated control
signal to the navigator 400. The magnetic resonance imaging
apparatus may further include an amplifier 920 to amplify an analog
magnetic resonance signal output from the RF coil unit 230. In
addition, the magnetic resonance imaging apparatus may further
include an A/D converter 930 to convert an analog signal output
from the amplifier 920 into a digital signal. The digitized
magnetic resonance signal is transmitted to the image generation
unit 500.
The image generation unit 500 receives the digitized magnetic
resonance signal output from the A/D converter 930 and motion
information (NAV data) output from the navigator 400, determines a
k-space data array using the received magnetic resonance signal and
motion information, and converts the determined k-space data to
generate a magnetic resonance image. Specifically, as shown in FIG.
14, the image generation unit 500 may include a k-space data
processing unit 600 to generate a k-space, a Fourier transform unit
510 to perform Fourier transform to the k-space, and an image
post-processing unit 520 to perform post-processing of the
Fourier-transformed magnetic resonance image.
FIG. 18 shows the k-space data processing unit 600 of the magnetic
resonance imaging apparatus including a first area processing unit
610, a second area processing unit 620, and an area combination
unit 630. The first area processing unit 610 acquires k-space data
of a central area of the k-space from a magnetic resonance signal.
Referring back to FIG. 7, for the magnetic resonance imaging
apparatus, a signal of each of the raw data has a signal of the
maximum amplitude at the central area of the k-space. When a
dephased proton is magnetized again, a magnetic resonance signal of
the maximum amplitude is output. When the proton is dephased again,
the amplitude is gradually decreased. As a result, the magnetic
resonance signal has a signal of the maximum amplitude at a column
located at the center of the data space as shown in FIG. 7. In
addition, since a signal of the row located at the center is
acquired without dephasing due to the gradient magnetic field Gy in
the y-axis direction, the amplitude is higher than those of signals
at the other rows. Amplitudes of signals at the other rows are
lower than that of the row located at the center due to the
gradient magnetic field Gy in the y-axis direction. As a result,
the magnetic resonance signal located at the center has the maximum
amplitude and signal to noise ratio (SNR). Consequently, the
strongest signal is present at the central area of the k-space. In
addition, signals at areas other than the central area are
relatively weak. The first area processing unit 610 collects
signals sg3 to sg5 (FIG. 7) at the central area at which the
strongest signal is present to acquire k-space data.
The first area processing unit 610 may acquire k-space data of the
central area of the k-space from the input magnetic resonance
signal where motion information output from the navigator 400 is
within a predetermined range, i.e. a k-space data collection range.
To this end, as shown in FIG. 18, the first area processing unit
610 may include an area determination unit 611, a motion
information determination unit 612, and a data acquisition unit
613. As shown in FIGS. 14 and 18, the area determination unit 611
of the first area processing unit 610 determines whether the
magnetic resonance signal received from the RF coil unit 230 is a
magnetic resonance signal for the central area of the k-space. Upon
determining that the magnetic resonance signal received from the RF
coil unit 230 is a magnetic resonance signal for the central area
of the k-space, the motion information determination unit 612 of
the first area processing unit 610 determines whether to acquire
k-space data based on the respiratory motion information, received
from the navigator 400.
For example, as shown in FIG. 8, the motion information
determination unit 612 may compare the input motion information
signals NAV1 and NAV2 with the k-space data acquisition range NAV
to determine whether the motion information signals NAV1 and NAV2
are within the k-space data acquisition range NAV and generate a
determination result signal. In this case, the motion information
determination unit 612 may select (gate) a signal having an
amplitude within a limited range from the motion information using
a gating window to sort only the motion information within the
-space data acquisition range and generate a determination result
signal based on the sorted motion information. The data acquisition
unit 613 collects k-space data for the central area of the k-space.
The data acquisition unit 613 may determine whether to collect
k-space data for the central area of the k-space according to the
determination result of the motion information determination unit
612.
When the motion information determination unit 612 determines that
the motion information is within a predetermined data acquisition
range, the data acquisition unit 613 extracts and stores a magnetic
resonance signal corresponding to the central area of the k-space
in acquiring k-space data for the central area of the k-space. When
the motion information determination unit 612 determines that the
motion information deviates from the predetermined data acquisition
range, the data acquisition unit 613 does not extract a magnetic
resonance signal. As a result, k-space data for the central area of
the k-space are not collected. For example, respiration motion is
tracked by the navigator 400 and a k-space data acquisition range
is defined as 7 mm, the data acquisition unit 613 acquires k-space
data for the central area of the k-space when the motion range
shown in FIG. 5 is less than 7 mm and does not collect k-space data
when the motion range shown in FIG. 5 is greater than 7 mm.
The second area processing unit 620 collects k-space data for the
area other than the central area of the k-space. Referring back to
FIG. 7, for the magnetic resonance imaging apparatus, the magnetic
resonance signal has the maximum amplitude at the central area of
the k-space and signals of areas other than the central area are
relatively weak. The second area processing unit 620 collects
signals sg1, sg2, sg6, and sg7 of the other areas at which the
signal are weak. As shown in FIG. 18, the second area processing
unit 620 may include an area determination unit 621 and a data
acquisition unit 622. The area determination unit 621 determines
whether the magnetic resonance image received from the data
collection unit 10 corresponds to the area other than the central
area of the k-space and if so, the second area processing unit 620
collects the magnetic resonance image signal to collect k-space
data for the area other than the central area of the k-space.
Unlike the first area processing unit 610, the second area
processing unit 620 does not determine whether additional motion
information is within the k-space data acquisition range.
The area combination unit 630 combines the k-space data for the
central area of the k-space acquired by the first area processing
unit 610 and the k-space data for the area other than the central
area of the k-space acquired by the second area processing unit 620
to form a k-space. As a result, a k-space K as shown in FIGS. 10
and 11 is formed. The central area K2 of the k-space is filled with
the k-space data acquired by the first area processing unit 610 and
the other areas K1 and K3 of the k-space is filled with the k-space
data acquired by the second area processing unit 620.
As shown in FIG. 14, the generated k-space is transmitted to the
Fourier transform unit 510 which converts the k-space into a
magnetic resonance image using Fourier transform. The
Fourier-transformed magnetic resonance image may be transmitted to
the image post-processing unit 520 as needed. The image
post-processing unit 520 adjusts brightness, sharpness, or contrast
of the entirety or a portion of the Fourier-transformed magnetic
resonance image to correct the Fourier-transformed magnetic
resonance image. The image post-processing unit 520 may generate a
three-dimensional stereoscopic image using a plurality of magnetic
resonance images. The magnetic resonance image, which is generated
or corrected as needed, is displayed outside through the display
unit d installed at the workstation w.
The data processing unit 600 may further include an area decision
unit 640 (FIG. 18). The area decision unit 640 may receive
information regarding areas to be processed by the first area
processing unit 610 and the second area processing unit 620 from a
manipulation unit i of an additional external workstation or an
additional memory device. As a result, a user may select and adjust
the size of the central area of the k-space, from which k-space
data is acquired in response to motion information. As needed, the
number or position of areas of the k-space may also be
adjusted.
FIG. 19 shows the k-space data processing unit of the magnetic
resonance imaging apparatus. A motion information determination
unit 612 of a first area processing unit 610 transmits a command
corresponding to a determination result to a signal generation unit
641. The signal generation unit 641 generates a control signal to
control the controller 300 according to the received command and
transmits the generated control signal to the controller 300. As
described previously, the motion information determination unit 612
compares the motion information received from the navigator 400
with the k-space data acquisition range. Upon determining that the
motion information deviates from the k-space data acquisition
range, the motion information determination unit 612 generates a
command based on the determination result and transmits the
generated command to the signal generation unit 641. For example,
referring back to FIG. 8, the motion information determination unit
612 compares input motion information signals NAV1 and NAV2 with a
k-space data acquisition range NAV defined by a user. Where the
motion information deviates from the k-space data acquisition range
as shown in the right side NB of FIG. 8 (NAV2), the motion
information determination unit 612 generates a control signal not
to acquire k-space data and transmits the control signal to a data
acquisition unit 613. The motion information determination unit 612
generates a command to generate a control signal for the controller
300 and transmits the command to the signal generation unit
641.
The signal generation unit 641 generates a control signal for the
controller 300 according to the determination result of the motion
information determination unit 612, i.e. the determination result
that the motion information deviates from the k-space data
acquisition range. The generated control signal is transmitted to
the controller 300. The controller 300 receives the control signal
from the signal generation unit 641 and controls operation of the
data collection unit 200 according to the received control signal.
Specifically, the static magnetic field controller 310, the
gradient magnetic field controller 320, and the RF coil controller
330 of the controller 300 may generate control signals for
operation of the static magnetic field coil unit 210, the gradient
magnetic field coil unit 220, and the RF coil unit 230 according to
the received control signal and transmit the generated control
signals to the static magnetic field coil unit 210, the gradient
magnetic field coil unit 220, and the RF coil unit 230. The static
magnetic field coil unit 210 and the gradient magnetic field coil
unit 220 apply a magnetic field to the object ob according to the
control signals such that the object ob, specifically the target
region in the object ob, is exposed to the magnetic field. The RF
coil unit 230 applies an electromagnetic wave to the target region
in the object ob to re-collect a magnetic resonance signal from the
target region inside or outside the object ob.
Where motion information received from the navigator 400 is not
within the k-space data acquisition range and thus the first area
processing unit 610 does not acquire k-space data, the data
collection unit 200 may re-collect a magnetic resonance signal from
the target region of the object ob. The re-collected magnetic
resonance signal is transmitted to the image generation unit 500,
specifically the k-space data processing unit 600, via the
amplifier 920 and the A/D converter 930. The k-space data
processing unit 600 may repeat a process of collecting or not
collecting k-space data from the re-collected magnetic resonance
signal according to the motion signal received from the navigator
400 and the areas of the k-space.
FIG. 20 shows another k-space data processing unit of the magnetic
resonance imaging apparatus including an area division unit 650.
The area division unit 650 may receive information regarding the
determined area of the k-space, e.g. the central area of the
k-space, from the area decision unit 640, identify and sort the
magnetic resonance signals from the RF coil unit 230 according to
the information of the received area of the k-space, and distribute
the magnetic resonance signals to the first area processing unit
610 or the second area processing unit 620. According to
embodiments, an amplifier 920 and an A/D converter 930 may be
further provided between the RF coil unit 230 and the area division
unit 650.
Specifically, the area decision unit 640 may determine areas of the
k-space to be processed by the first area processing unit 610 and
the second area processing unit 620 according to user command input
through the manipulation unit i or pre-stored setting information.
For example, the area decision unit 640 may determine the central
area of the k-space as a first area and the area other than the
central area as a second area. When the area of the k-space is
determined by the area decision unit 640 as described above, the
area division unit 650 may sort a magnetic resonance signal
corresponding to the first area, e.g. the central area of the
k-space, i.e. first area data, and a magnetic resonance signal
corresponding to the second area, e.g. the area other than the
central area of the k-space, i.e. second area data, from the
magnetic resonance signals input from the RF coil unit 230
according to the determined area of the k-space.
The area division unit 650 transmits the first area data to the
first area processing unit 610 and transmits the second area data
to the second area processing unit 620. The first area data and the
second area data may be sorted at the same time or at different
times. Alternatively, the first area data and the second area data
may be sequentially sorted. For example, the area decision unit 640
may determine whether the magnetic resonance signal is a magnetic
resonance signal corresponding to a portion of the k-space which is
pre-determined, e.g. the central area of the k-space, and, upon
determining that the magnetic resonance signal is a magnetic
resonance signal corresponding to a portion of the k-space which is
pre-determined, transmits the magnetic resonance signal to the
first area processing unit 610. Upon determining that the magnetic
resonance signal does not correspond to a portion of the k-space
which is pre-determined, the area decision unit 640 may determine
whether the magnetic resonance signal corresponds to another
portion of the k-space which is pre-determined, and, upon
determining that the magnetic resonance signal corresponds to
another portion of the k-space which is pre-determined, transmit
the magnetic resonance signal to the second area processing unit
620. The area division unit 650 may determine whether the magnetic
resonance signal corresponds to a further portion of the k-space
which is pre-determined and transmits the magnetic resonance signal
to a third area processing unit. The area division unit 650 may be
omitted in an embodiment, for example, where the first area data
and the second area data are already divided and are input to the
k-space data processing unit 600.
FIGS. 21 and 22 show magnetic resonance images generated by the
image generation unit 500. The upper row of images are magnitude
and the lower row of images are phase contrast flow images. A
magnetic resonance image acquired using a full gating method to
collect k-space data where motion information regarding the entire
area of the k-space is within a predetermined range is shown in
FIG. 22. As shown in FIGS. 21 and 22, there is no great difference
between the two images, however, acquisition time of the k-space is
advantageously reduced.
For example, acquisition time of the k-space using a full gating
method is about 19 minutes 35 seconds.+-.5 minutes 2 seconds.
Whereas, the acquisition time of the k-space according to the
magnetic resonance imaging apparatus is about 13 minutes 19
seconds.+-.3 minutes 2 seconds. That is, the acquisition time of
the k-space using the full gating method is reduced by about 30%.
Consequently, an image of substantially the same quality may be
acquired within reduced time, and navigator gating efficiency is
improved. The magnetic resonance imaging is usable by different
kinds of magnetic resonance imaging using a navigator echo such as
cardiac magnetic resonance imaging. In addition, the magnetic
resonance imaging apparatus as described above may also be applied
to various kinds of magnetic resonance imaging apparatuses to
perform cardiac flow imaging, coronary MO angiography, cardiac
perfusion imaging, and cardiac late gadolinium enhancement (LGE)
imaging.
A k-space generation method and a control method of the magnetic
resonance imaging apparatus is described with reference to FIGS. 23
to 27. FIG. 23 shows a k-space generation method. As shown in FIG.
23, in order to collect k-space data from raw data and to generate
a k-space using the collected k-space data, raw image data are
collected from a target region (S710) and motion information is
collected from a motion region at the same time or at different
times (S711). In a case in which the collected raw image data for
the target region are raw image data corresponding to a first area
of the k-space (S713), it is determined whether the motion
information collected from the motion region is within a k-space
data acquisition range (S714). The k-space data acquisition range
may be selected by a user or pre-determined and stored. In this
case, as shown in FIG. 23, it may be determined whether the
collected raw image data for the target region is image data
corresponding to a portion of the k-space which is pre-determined,
i.e. a first area of the k-space, before the space data acquisition
range is determined (S712).
Upon determining that the motion information collected from the
motion region is within the k-space data acquisition range (S715),
the raw image data are stored to acquire k-space data to fill the
first area of the k-space (S716). Upon determining at Operation
S713 that the collected raw image data is not image data
corresponding to the first area of the k-space but are image data
corresponding to a second area of the k-space (S718), the raw image
data corresponding to the second area of the k-space is stored to
acquire k-space data for the second area of the k-space (S719). In
operation S713 if the collected raw image data is not image data
corresponding to the first area of the k-space, it may be
determined whether the collected raw image data are image data
corresponding to the second area of the k-space (S717). When the
k-space data for the first area and the second area of the k-space
are collected, the k-space data for the first area of the k-space
and the space data for the second area of the k-space are combined
to acquire a final k-space (S720).
FIG. 24 another k-space generation method where motion information
deviates from a k-space data acquisition range. Image data and
motion information are collected from a target region and a motion
region, respectively (S720 and S721) and it is determined whether
the motion information is within a k-space data acquisition range
(S723). Upon determining that the motion information is within the
k-space data acquisition range, k-space data for a first area are
stored and acquired as described above and the k-space data for the
first area and k-space data for a second area acquired using the
above method are combined to acquire a final k-space (S723 to
S727). Upon determining that the motion information is not within
the k-space data acquisition range, i.e. the motion information
deviates from the k-space data acquisition range, k-space data are
not acquired from the image data. In this case, the collected raw
image data may be discarded (S728). Subsequently, raw image data
for the target region are re-collected from the target region
(S729). In this case, at Operation S729, raw image data for the
target region may be re-collected using a method identical or
similar to the image data collection method (S720) as described
above. Alternatively, raw image data for the target region may be
re-collected using a method different from the image data
collection method.
FIG. 25 shows a control method of the magnetic resonance imaging
system. An object ob, e.g. a human body, is introduced into the
bore of the magnetic resonance imaging apparatus via a transfer
table (S730). The static magnetic field coil unit 210 and the
gradient magnetic field coil unit 220 of the magnetic resonance
imaging apparatus generate and apply magnetic fields to the object
ob such that the object is exposed to the magnetic fields (S731).
When the RF coil unit 230 applies an electromagnetic wave to a
target region of the object ob exposed to the magnetic fields
(S732), a magnetic resonance excitation is generated in a hydrogen
atom of the target region in the object ob (S733). The RF coil unit
230 collects magnetic resonance signals from the target region of
the object (S734).
The image generation unit 500 of the magnetic resonance imaging
apparatus receives the magnetic resonance signals from the RF coil
unit 230 (S735). Motion information regarding the motion region of
the human body, e.g. motion information regarding the chest
performing respiration, is collected by the navigator 400. The
image generation unit 500 determines whether, for a magnetic
resonance signal corresponding to a first area of a k-space, e.g. a
central area of the k-space, among the received magnetic resonance
signals (S740), the motion information regarding the motion region
of the object ob acquired from the navigator 400 is within a
k-space data acquisition range (S742). Upon determining that the
acquired motion information is within the k-space data acquisition
range (S743), the image generation unit 500 stores the magnetic
resonance signal to acquire k-space data for the first area of the
k-space (S744). For a magnetic resonance signal corresponding to a
second area of the k-space, e.g. an area other than the central
area of the k-space, among the received magnetic resonance signals
(S750), the image generation unit 500 stores the magnetic resonance
signal without consideration of the motion information to acquire
k-space data for the second area of the k-space (S751). When the
k-space data for the first area of the k-space and the space data
for the second area of the k-space are collected, the k-space data
for the first area of the k-space and the space data for the second
area of the k-space are combined (S760) to acquire a final k-space
(S761). The image generation unit 500 performs Fourier transform to
the acquired k-space to generate a magnetic resonance image and
transmits the generated magnetic resonance image to the display
unit such that a user may view the magnetic resonance image.
FIG. 26 another control method of the magnetic resonance imaging
system Where motion information acquired from the navigator 400 is
not within the k-space data acquisition range. In response to
k-space data being acquired from a magnetic resonance signal
corresponding to the first area of the k-space, among the received
magnetic resonance signals (S771 to S773), the magnetic resonance
signal may not be stored but may be discarded. As a result, k-space
data for the first area of the k-space may not be acquired
(S775).
In this case, the image generation unit 500 generates a control
signal to re-collect data (S776) and transmits the control signal
to the controller 300 (S777). The controller further generates a
control signal to control the RF coil unit 230 to re-apply an
electromagnetic wave to the target region of the object. The RF
coil unit 230 applies an electromagnetic wave to the target region
in the object ob exposed to the magnetic field to re-receive and
re-collect a magnetic resonance signal (S778). Where motion
information acquired from the navigator 400 is within the k-space
data acquisition range, the magnetic resonance signal is stored to
acquire k-space data (S774).
FIG. 27 shows a further control method of the magnetic resonance
imaging system. The data collection unit 220 collects a plurality
of magnetic resonance signals (S780) and transmits the collected
magnetic resonance signals to the image generation unit. The image
generation unit may receive the magnetic resonance signals (S781)
and determines to which areas of the k-space the received the
magnetic resonance signals correspond (S782). This determination
may be performed by the area division unit 650. In response to
determining that the magnetic resonance signal is a magnetic
resonance signal corresponding to the first area of the k-space,
e.g. the central area of the k-space (S783), it is determined
whether additionally collected motion information is within a
k-space data acquisition range (S785). Upon determining that the
collected motion information is within the k-space data acquisition
range (S786), a magnetic resonance image is extracted and stored in
acquiring k-space data from the first area of the k-space (S787).
Upon determining that the collected motion information is not
within the k-space data acquisition range (S786), the magnetic
resonance image is not stored but discarded (S788).
Upon determining that the magnetic resonance signal is not a
magnetic resonance signal corresponding to the first area of the
k-space, it may be determined whether the magnetic resonance signal
is a magnetic resonance signal corresponding to the second area of
the k-space (S790). Upon determining that the magnetic resonance
signal is a magnetic resonance signal corresponding to the second
area of the k-space, the magnetic resonance signal is stored
without additional conditions in acquiring k-space data from the
second area of the k-space (S791). Upon determining that the
magnetic resonance signal is not a magnetic resonance signal
corresponding to the second area of the k-space, the collected
magnetic resonance signal is discarded (S792). In response to
collection of the k-space data for the first area and the second
area, the k-space data for the first area of the k-space and the
space data for the second area of the k-space are combined to
generate a k-space (S793). As a result, a final k-space is
acquired.
The system improves diagnosis of lesions of a human body using a
magnetic resonance image, therefore, reliability of diagnosis is
improved and the rate of misdiagnosis is reduced. Although a few
embodiments of the present invention have been shown and described,
it would be appreciated by those skilled in the art that changes
may be made in these embodiments without departing from the
principles and spirit of the invention, the scope of which is
defined in the claims and their equivalents.
The above-described embodiments can be implemented in hardware,
firmware or via the execution of software or computer code that can
be stored in a recording medium such as a CD ROM, a Digital
Versatile Disc (DVD), a magnetic tape, a RAM, a floppy disk, a hard
disk, or a magneto-optical disk or computer code downloaded over a
network originally stored on a remote recording medium or a
non-transitory machine readable medium and to be stored on a local
recording medium, so that the methods described herein can be
rendered via such software that is stored on the recording medium
using a general purpose computer, or a special processor or in
programmable or dedicated hardware, such as an ASIC or FPGA. As
would be understood in the art, the computer, the processor,
microprocessor controller or the programmable hardware include
memory components, e.g., RAM, ROM, Flash, etc. that may store or
receive software or computer code that when accessed and executed
by the computer, processor or hardware implement the processing
methods described herein. In addition, it would be recognized that
when a general purpose computer accesses code for implementing the
processing shown herein, the execution of the code transforms the
general purpose computer into a special purpose computer for
executing the processing shown herein. The functions and process
steps herein may be performed automatically or wholly or partially
in response to user command. An activity (including a step)
performed automatically is performed in response to executable
instruction or device operation without user direct initiation of
the activity. No claim element herein is to be construed under the
provisions of 35 U.S.C. 112, sixth paragraph, unless the element is
expressly recited using the phrase "means for."
* * * * *